Thermally enhanced semiconductor package with at least one heat extractor and process for making the same

ABSTRACT

The present disclosure relates to a thermally enhanced package, which includes a carrier, a thinned die over the carrier, a mold compound, and a heat extractor. The thinned die includes a device layer over the carrier and a dielectric layer over the device layer. The mold compound resides over the carrier, surrounds the thinned die, and extends beyond a top surface of the thinned die to define an opening within the mold compound and over the thinned die. The top surface of the thinned die is at a bottom of the opening. At least a portion of the heat extractor is inserted into the opening and in thermal contact with the thinned die. Herein the heat extractor is formed of a metal or an alloy.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 16/204,214, filed Nov. 29, 2018, the disclosure of which is hereby incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a package and a process for making the same, and more particularly to a thermally enhanced package, and a process to apply at least one heat extractor into the package for enhanced thermal performance.

BACKGROUND

With the current popularity of portable communication devices and developed fabrication technology, high speed and high performance transistors are more densely integrated on device modules. Consequently, the amount of heat generated by the device modules will increase significantly due to the large number of transistors integrated on the device modules, the large amount of power passing through the transistors, and the high operation speed of the transistors. Accordingly, it is desirable to package the device modules in a configuration for better heat management.

Conventionally, these high-power device modules may reside directly over heat sinks for heat evacuation. However, such assemblies are not attractive for the low profile applications. In some applications, the heat sinks may be embedded in a printed circuit board (PCB). A superior thermal conductance between the high-power device modules and the heat sinks within the PCB is required. Furthermore, the heat sinks embedded in the PCB may block electrical routing in the PCB to ensure the thermal sinking capability.

To accommodate the increased heat generation of the device modules, it is therefore an object of the present disclosure to provide an improved package design with enhanced thermal performance. Further, there is also a need to enhance the performance of the device modules without increasing the package size or sacrificing the electrical performance.

SUMMARY

The present disclosure relates to a thermally enhanced package, and a process for making the same. The disclosed thermally enhanced package includes a carrier having a top surface, a first thinned die, a first mold compound, and a first heat extractor. The first thinned die includes a first device layer over the top surface of the carrier and a first dielectric layer over the first device layer. The first mold compound resides on the top surface of the carrier, surrounds the first thinned die, and extends beyond a top surface of the first thinned die to define a first opening within the first mold compound and over the first thinned die. Herein, the first mold compound does not reside over the first thinned die and provides vertical walls of the first opening, which are aligned with edges of the first thinned die in both X-direction and Y-direction. The X-direction and the Y-direction are parallel to the top surface of the carrier, and the X-direction and the Y-direction are orthogonal to each other. The top surface of the first thinned die is at a bottom of the first opening. In addition, at least a portion of the first heat extractor is inserted into the first opening and in thermal contact with the first thinned die. The first heat extractor is formed of a metal or an alloy.

In one embodiment of the thermally enhanced package, a top surface of the first dielectric layer is the top surface of the first thinned die.

In one embodiment of the thermally enhanced package, the first heat extractor is attached to the first thinned die via an attach layer, which is formed of thermal conductive epoxies, thermal conductive silicones, or alumina thermal adhesives.

In one embodiment of the thermally enhanced package, the first heat extractor has both an X-direction dimension and a Y-direction dimension essentially the same as the first thinned die.

In one embodiment of the thermally enhanced package, the first heat extractor fully fills the first opening. A top surface of the first heat extractor and a top surface of the first mold compound are essentially at a same plane.

In one embodiment of the thermally enhanced package, the top surface of the first heat extractor is lower than the top surface of the first mold compound.

According to another embodiment, the thermally enhanced package further includes a second heat extractor. Herein, at least a portion of the second heat extractor is inserted in the first opening and over the first heat extractor. The second heat extractor, the first heat extractor, and the first thinned die are thermally connected.

In one embodiment of the thermally enhanced package, the second heat extractor is attached to the first heat extractor via an attach layer, which is formed of thermal conductive epoxies, thermal conductive silicones, or alumina thermal adhesives.

In one embodiment of the thermally enhanced package, the first thinned die further includes a number of interconnects extending from a bottom surface of the first device layer to the top surface of the carrier.

According to another embodiment, the thermally enhanced package further includes an underfilling layer, which resides between the first mold compound and the top surface of the carrier, and underfills the first thinned die between the bottom surface of the first device layer and the top surface of the carrier. The underfilling layer is formed from a same material as the first mold compound.

In one embodiment of the thermally enhanced package, the carrier includes a number of antenna patches at a bottom surface of the carrier. Each antenna patch is electrically connected to a corresponding interconnect.

In one embodiment of the thermally enhanced package, the carrier is one of a laminate carrier, a wafer level fan out (WLFO) carrier, a wafer level fan in (WLFI) carrier, a lead frame, and a ceramic carrier.

According to another embodiment, the thermally enhanced package further includes a second thinned die with a second device layer over the top surface of the carrier and a second dielectric layer over the second device layer. Herein, the first mold compound surrounds the second thinned die, and extends beyond a top surface of the second thinned die to define a second opening within the first mold compound and over the second thinned die. The first mold compound does not reside over the second thinned die and provides vertical walls of the first opening, which are aligned with edges of the second thinned die in both the X-direction and the Y-direction. The top surface of the second thinned die is at a bottom of the second opening. A first portion of the first heat extractor is inserted in the first opening and in thermal contact with the first thinned die, and a second portion of the first heat extractor is inserted in the second opening and in thermal contact with the second thinned die. The first heat extractor has a multi-finger comb-structure.

In one embodiment of the thermally enhanced package, the carrier includes a number of carrier contacts at the top surface of the carrier. Each interconnect is electrically connected to a corresponding carrier contact.

According to another embodiment, the thermally enhanced package further includes at least one through mold via (TMV), which is electrically connected to the first thinned die via a corresponding carrier contact and extends through the first mold compound from a bottom surface of the first mold compound to a top surface of the first mold compound.

According to another embodiment, the thermally enhanced package is included in a system assembly. Beside the thermally enhanced package, the system assembly further includes a printed circuit board (PCB) with at least one board contact on a bottom surface of the PCB. Herein, the bottom surface of the PCB is over the top surface of the first mold compound, and the at least one TMV is electrically connected to the at least one board contact via at least one solder pad or at least one solder ball.

In one embodiment of the system assembly, the PCB further includes a heat sink structure on the bottom surface of the PCB. The heat sink structure is in thermal contact with the first heat extractor in the thermally enhanced package.

According to another embodiment, the thermally enhanced package further includes a second mold compound, which is formed over the first mold compound and encapsulates the first heat extractor. Herein, the at least one TMV extends through the first mold compound and the second mold compound. There is at least one solder pad or at least one solder ball formed over the second mold compound and electrically connected to the at least one TMV.

According to an exemplary process, a precursor package, which includes a carrier, a first die attached to a top surface of the carrier, and a first mold compound, is provided. The first mold compound is formed over the top surface of the carrier and encapsulates the first die. Herein, the first die includes a first device layer, a first dielectric layer over the first device layer, and a first die substrate over the first dielectric layer. The first mold compound is then thinned down to expose a backside of the first die substrate. Next, the entire first die substrate is removed to create a first opening within the first mold compound and provide a first thinned die. The first opening is formed over the first thinned die, and a top surface of the first thinned die is at a bottom of the first opening. Finally, at least a portion of a heat extractor, which is formed of a metal, is inserted into the first opening, such that the heat extractor is in thermal contact with the first thinned die.

Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

FIG. 1 shows an exemplary thermally enhanced package according to one embodiment of the present disclosure.

FIGS. 2-8 shows an alternative thermally enhanced package according to one embodiment of the present disclosure.

FIGS. 9A-9E provide exemplary steps that illustrate a process to fabricate the exemplary thermally enhanced package shown in FIG. 1.

It will be understood that for clear illustrations, FIGS. 1-9E may not be drawn to scale.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being “over” or extending “over” another element, it can be directly over or extend directly over the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly over” or extending “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.

Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The present disclosure relates to a thermally enhanced package, and a process for making the same. FIG. 1 shows an exemplary thermally enhanced package 10 according to one embodiment of the present disclosure. For the purpose of this illustration, the exemplary thermally enhanced package 10 includes a carrier 12, a first thinned die 14, an underfilling layer 16, a first mold compound component 18, a first heat extractor 20, and a first attach layer 22. In different applications, the thermally enhanced package 10 may include multiple thinned dies.

In detail, the carrier 12 may be a laminate carrier, a wafer level fan out (WLFO) carrier, a wafer level fan in (WLFI) carrier, a lead frame, or a ceramic carrier, or the like. The carrier 12 includes a number of first carrier contacts 24 (only one first carrier contact is labeled with a reference number for clarity) formed at a top surface of the carrier 12 and configured to electrically connect to the first thinned die 14. The first thinned die 14 includes a first device layer 26, a first dielectric layer 28 over a top surface of the first device layer 26, and a number of first interconnects 30 (only one first interconnect is labeled with a reference number for clarity) extending from a bottom surface of the first device layer 26 to the top surface of the carrier 12. Herein, each first interconnect 30 is electrically connected to a corresponding first carrier contact 24. The first device layer 26 with a thickness between 10 nm and 20000 nm may be formed of silicon oxide, gallium arsenide, gallium nitride, silicon germanium, or the like. The first dielectric layer 28 with a thickness between 10 nm and 20000 nm may be formed of silicon oxide, silicon nitride, or aluminum nitride. The first interconnects 30 with a height between 5 μm and 200 μm may be copper pillar bumps, solder ball bumps, or the like.

In one embodiment, the first thinned die 14 may be formed from a silicon-on-insulator (SOI) structure, which refers to a structure including a silicon substrate, a silicon epitaxy layer, and a buried oxide (BOX) layer sandwiched between the silicon substrate and the silicon epitaxy layer. The first device layer 26 of the first thinned die 14 is formed by integrating electronic components (not shown) in or on the silicon epitaxy layer of the SOI structure. The first dielectric layer 28 of the first thinned die 14 is the BOX layer of the SOI structure. In addition, the silicon substrate of the SOI structure is removed substantially to complete the first thinned die 14 (more details in the following discussion). In some applications, a top surface of the first thinned die 14 may be a top surface of the first dielectric layer 28.

The underfilling layer 16 resides over the top surface of the carrier 12, such that the underfilling layer 16 encapsulates the first interconnects 30 and underfills the first thinned die 14 between the bottom surface of the first device layer 26 and the top surface of the carrier 12. The underfilling layer 16 may be formed from conventional polymeric compounds, which serve to mitigate the stress effects caused by Coefficient of Thermal Expansion (CTE) mismatch between the first thinned die 14 and the carrier 12.

The first mold compound component 18 resides over the underfilling layer 16, surrounds the first thinned die 14, and extends beyond the top surface of the first thinned die 14 to define a first opening 32 within the first mold compound 18 and over the first thinned die 14. The top surface of the first thinned die 14 is at a bottom of the first opening 32. Herein, the first mold compound 18 does not reside over the first thinned die 14 and provides vertical walls of the first opening 32 in Z-direction. The vertical walls of the first opening 32 are well aligned with edges of the first thinned die 14 in both X-direction and Y-direction. Herein, the X-direction and the Y-direction are parallel to the top surface of the carrier 12, and the Z-direction is perpendicular to the top surface of the carrier 12. The X-direction, the Y-direction, and the Z-direction are all orthogonal to each other. The first mold compound 18 may be formed from a same or different material as the underfilling layer 16. When the first mold compound 18 and the underfilling layer 16 are formed from a same material, the first mold compound 18 and the underfilling layer 16 may be formed simultaneously. One exemplary material used to form the first mold compound 18 is an organic epoxy resin system.

In addition, at least a portion of the first heat extractor 20 is inserted into the first opening 32 and attached to the top surface of the first thinned die 14 via the first attach layer 22. The first heat extractor 20 may be a metal slug that has a large thermal radiating area. The first heat extractor 20 may be formed of copper, aluminum/aluminum alloys, brass, or other metals or alloys that have a high thermal conductivity. The first attach layer 22 may be formed of thermal adhesives or thermal greases, such as thermal conductive epoxies, thermal conductive silicones, alumina thermal adhesives or other materials that can intermediate the thermal interface between the first thinned die 14 and the first heat extractor 20. Various viscosities, hardnesses, and cure speed specifications of the first attach layer 22 are available. As such, the first heat extractor 20 is in thermal contact with the first thinned die 14, and configured to absorb heat generated from the first thinned die 14. For the purpose of this illustration, the first heat extractor 20 has both an X-direction dimension and a Y-direction dimension essentially the same as the first thinned die 14, and the first heat extractor 20 has a thickness (in Z-direction dimension) essentially the same as a depth of the first opening 32. Herein, essentially the same refers to between 95% and 100%. In detail, the X-direction dimension of the first heat extractor 20 may be between 95% and 100% of the X-direction dimension of the first thinned die 14, and the Y-direction dimension of the first heat extractor 20 may be between 95% and 100% of the Y-direction dimension of the first thinned 14. As such, the first heat extractor 20 fully fills the first opening 32, and a top surface of the first heat extractor 20 and a top surface of the first mold compound 18 are essentially at a same plane. In different applications, the thickness of the first heat extractor 20 may be different from the depth of the first opening 32, such that the top surface of the first heat extractor 20 may be lower or higher than the top surface of the first mold compound 18 (not shown here).

In these cases where the thickness of the first heat extractor 20 is shorter than the depth of the first opening 32, the thermally enhanced package 10 may further include a second heat extractor 34 and a second attach layer 36, as illustrated in FIG. 2. Herein, the first heat extractor 20 resides within a lower region of the first opening 32, and at least a portion of the second heat extractor 34 is inserted into an upper region of the first opening 32 and attached to the top surface of the first heat extractor 20 via the second attach layer 36. The second heat extractor 34 may be a metal slug that has a large thermal radiating area. The second heat extractor 34 may be formed of copper, aluminum/aluminum alloys, brass, or other metals or alloys that have a high thermal conductivity. The second attach layer 36 may be formed of thermal adhesives or thermal greases, such as thermal conductive epoxies, thermal conductive silicones, alumina thermal adhesives, or other materials that can intermediate the thermal interface between the first heat extractor 20 and the second heat extractor 34. Various viscosities, hardnesses, and cure speed specifications of the second attach layer 36 are available. Herein, the second heat extractor 34, the first heat extractor 20, and the first thinned die 14 are thermally connected. A combination of the first heat extractor 20 and the second heat extractor 34 is configured to absorb heat generated from the first thinned die 14. For the purpose of this illustration, the second heat extractor 36 has both an X-direction dimension and a Y-direction dimension essentially the same as the first thinned die 14. A combined thickness of the first heat extractor 20 and the second heat extractor 36 is essentially the same as the depth of the first opening 32. As such, a top surface of the second heat extractor 34 and the top surface of the first mold compound 18 are essentially at a same plane.

In some applications, the thermally enhanced package 10 includes multiple thinned dies, as illustrated in FIG. 3. Herein, besides the first thinned die 14, the thermally enhanced package 10 also includes a second thinned die 38. The second thinned die 38 includes a second device layer 40, a second dielectric layer 42 over a top surface of the second device layer 40, and a number of second interconnects 44 (only one second interconnect is labeled with a reference number for clarity) extending from a bottom surface of the second device layer 40 to the top surface of the carrier 12. The second device layer 40 with a thickness between 10 nm and 20000 nm may be formed of silicon oxide, gallium arsenide, gallium nitride, silicon germanium, or the like. The second dielectric layer 42 with a thickness between 10 nm and 20000 nm may be formed of silicon oxide, silicon nitride, or aluminum nitride. The second interconnects 44 with a height between 5 μm and 200 μm may be copper pillar bumps, solder ball bumps, or the like.

The underfilling layer 16 encapsulates the second interconnects 44 and underfills the second thinned die 38 between the bottom surface of the second device layer 40 and the top surface of the carrier 12. The first mold compound 18 resides over the underfilling layer 16, surrounds the second thinned die 38, and extends beyond a top surface of the second thinned die 38 to define a second opening 46 within the first mold compound 18. The second opening 46 is over the second thinned die 38 and the top surface of the second thinned die 38 is at a bottom of the second opening 46. Herein, the first mold compound 18 does not reside over the second thinned die 38 and provides vertical walls of the second opening 46 in the Z-direction. The vertical walls of the second opening 46 are well aligned with edges of the second thinned die 38 in both the X-direction and the Y-direction.

In this embodiment, a first portion of the first heat extractor 20-1 is inserted in the first opening 32 and in thermal contact with the first thinned die 14, and a second portion of the first heat extractor 20-2 is inserted in the second opening 46 and in thermal contact with the second thinned die 38. The first heat extractor 20 may have a “multi-finger comb-structure” (also described in some cases as a combined-T shape). Notice that the first heat extractor 20 may be a metal slug, a metal comb, or other suitable structures that have a large thermal radiating area. The first portion of the first heat extractor 20-1 is attached to the top surface of the first thinned die 14 via the first attach layer 22, and the second portion of the first heat extractor 20-2 is attached to the top surface of the second thinned die 38 via a third attach layer 48. The third attach layer 48 may be formed of thermal adhesives or thermal greases, such as thermal conductive epoxies, thermal conductive silicones, alumina thermal adhesives or other materials that can intermediate the thermal interface between the second thinned die 38 and the second portion of the first heat extractor 20-2. Various viscosities, hardnesses, and cure speed specifications of the third attach layer 48 are available. The first portion of the first heat extractor 20-1 is configured to absorb heat generated from the first thinned die 14, while the second portion of the first heat extractor 20-2 is configured to absorb heat generated from the second thinned die 38.

Furthermore, the carrier 12 also includes a number of second carrier contacts 50 (only one second carrier contact is labeled with a reference number for clarity), which are formed at the top surface of the carrier 12 and configured to electrically connect to the second thinned die 38. Each second interconnect 44 is electrically connected to a corresponding second carrier contact 50.

In one embodiment, the second thinned die 38 may be formed from a silicon-on-insulator (SOI) structure. The second device layer 40 of the second thinned die 38 is formed by integrating electronic components (not shown) in or on the silicon epitaxy layer of the SOI structure. The second dielectric layer 42 of the second thinned die 38 is the BOX layer of the SOI structure. In addition, the silicon substrate of the SOI structure is removed substantially to complete the second thinned die 38. In some applications, a top surface of the second thinned die 38 is a top surface of the second dielectric layer 42.

In some applications, the carrier 12 may further include a number of antenna patches 52 at a bottom surface of the carrier 12 to provide an antenna array, as illustrated in FIG. 4. Herein, each antenna patch 52 may be electrically connected to a corresponding first carrier contact 24 by one carrier via 54 (only one antenna patch and one carrier via are labeled with reference numbers for clarity). Consequently, each antenna patch 52 is electrically connected to the first thinned die 14. The antenna patches 52 formed at the bottom surface of the carrier 12 ensures a minimal length for the interconnection between the first thinned die 14 and the antenna array. The antenna patches 52 may be formed of metal plates, built out of copper, aluminum/aluminum alloys, TLCC materials, or other metals or alloys that have a high electrical conductivity for low insertion loss. If the carrier 12 is a WLFO carrier or a WLFO carrier, the first carrier contacts 24, the carrier vias 54, and the antenna patches 52 may be realized when redistribution layers (RDL) are formed in the carrier 12.

FIGS. 5 and 6 show that the thermally enhanced package 10 further includes a second mold compound 56 to close the first heat extractor 20. The second mold compound 56 is formed over the first mold compound 18 and the first opening 32. Regardless of the thickness of the first heat extractor 20 (the top surface of the first heat extractor 20 may be higher than, lower than, or at a same plane level as the top surface of the first mold compound 18), the second mold compound 56 completely encapsulates and directly connects to the first heat extractor 20. The second mold compound 56 is a high thermal conductivity mold compound. Compared to the normal mold compound having 1 w/m·k thermal conductivity, a high thermal conductivity mold compound has 2.5 w/m·k˜10 w/m·k or greater thermal conductivity. The second mold compound 56 may be formed of thermoplastics or thermoset materials, such as PPS (poly phenyl sulfide), overmold epoxies doped with boron nitride or alumina thermal additives, or the like. The second mold compound 56 may be formed of a same or different material as the first mold compound 18. However, unlike the second mold compound 56, the first mold compound 18 does not have thermal conductivity requirements.

In addition, the thermally enhanced package 10 may further include one or more through mold vias (TMVs) 58, which provide electric connectivity to the first thinned die 14. Each TMV 58 is electrically connected to the first thinned die 14 via a corresponding first carrier contact 24, and extends through the underfilling layer 16, the first mold compound 18, and the second mold compound 56. If the carrier 12 includes the antenna patches 52, the TMVs 58 may electrically connected to the antenna patches 52. There may be solder pads 60 (FIG. 5) or solder balls 62 (FIG. 6) formed over the second mold compound 56 and electrically connected to the corresponding TMVs 58.

FIG. 7 shows a system assembly 64 including the thermally enhanced package 10. In this embodiment, the thermally enhanced package 10 may not include the second mold compound 56 to encapsulate the first heat extractor 20, such that the TMVs 58 only extend through the underfilling layer 16 and the first mold compound 18. Each solder pad 60 is formed over the first mold compound 18 and electrically connected to the corresponding TMV 58. Besides the thermally enhanced package 10, the system assembly 64 also includes a printed circuit board (PCB) 66 with a number of board contacts 68 at a bottom surface of the PCB 66. The PCB 66 resides over the thermally enhanced package 10 and each solder pad 60 on the first mold compound 18 is electrically connected to a corresponding board contact 68. Furthermore, the PCB 66 may also include a heat sink structure 70 at the bottom surface of the PCB 66, which is in thermal contact with the first heat extractor 20 via a thermal attach layer 72. The thermal attach layer 72 may be formed of thermal adhesives or thermal greases, such as thermal conductive epoxies, thermal conductive silicones, alumina thermal adhesives, or other materials that can intermediate the thermal interface between the first heat extractor 20 and the heat sink structure 70. Various viscosities, hardnesses, and cure speed specifications of the thermal attach layer 72 are available. The thermal attach layer 72 may have a thermal conductivity more than 0.5 w/m·k, or between 1 w/m·k and 3 w/m·k. If the PCB 66 does not include a heat sink structure 70, there may be no need to thermally couple the first heat extractor 20 to the PCB 66. In some applications, the solder balls 62 instead of the solder pads 60 are used to electrically connect the TMVs 58 to corresponding board contacts 68, as illustrated in FIG. 8. The sink structure 70 in the PCB 66 and the thermal attach layer 72 may be omitted.

FIGS. 9A-9E provide exemplary steps that illustrate a process to fabricate the exemplary thermally enhanced package 10 shown in FIG. 1. Although the exemplary steps are illustrated in a series, the exemplary steps are not necessarily order dependent. Some steps may be done in a different order than that presented. Further, processes within the scope of this disclosure may include fewer or more steps than those illustrated in FIGS. 9A-9E. If the carrier 12 is a laminate carrier, the exemplary steps are fabricated in a module level. If the carrier 12 is a WLFO carrier or a WLFI carrier, the exemplary steps are fabricated in a wafer level.

Initially, a precursor package 74 is provided as depicted in FIG. 9A. For the purpose of this illustration, the precursor package 74 includes the carrier 12 with the first carrier contacts 24, a first die 14D, the underfilling layer 16, and the first mold compound component 18. In different applications, the precursor package 74 may include multiple dies. Herein, the first die 14D includes the first device layer 26, the first dielectric layer 28 over the top surface of the first device layer 26, the first interconnects 30 (only one first interconnect is labeled with a reference number for clarity) extending from the bottom surface of the first device layer 26 to the top surface of the carrier 12, and a first die substrate 76 over the top surface of the first dielectric layer 28. As such, a backside of the first die substrate 76 is a top surface of the first die 14D. Herein, each of the first interconnects 30 is electrically connected to a corresponding first carrier contact 24 in the carrier 12.

In one embodiment, the first die 14D may be formed from a SOI structure. The first device layer 26 of the first die 14D is formed by integrating electronic components (not shown) in or on the silicon epitaxy layer of the SOI structure. The first dielectric layer 28 of the first die 14D is the BOX layer of the SOI structure. The first die substrate 76 of the first die 14D is the silicon substrate of the SOI structure. The first die 14D has a thickness between 25 μm and 250 μm or between 25 μm and 750 μm, and the first die substrate 76 has a thickness between 25 μm and 250 μm or between 25 μm and 750 μm, respectively.

In addition, the underfilling layer 16 resides over the top surface of the carrier 12, such that the underfilling layer 16 encapsulates the first interconnects 30 and underfills the first die 14D between the bottom surface of the first device layer 26 and the top surface of the carrier 12. The first mold compound 18 resides over the underfilling layer 16 and encapsulates the first die 14D. The first mold compound 18 may be used as an etchant barrier to protect the first die 14D against etching chemistries such as Tetramethylammonium hydroxide (TMAH), potassium hydroxide (KOH), sodium hydroxide (NaOH), and acetylcholine (ACH) in the following steps.

Next, the first mold compound 18 is thinned down to expose the backside of the first die substrate 76 of the first die 14D, as shown in FIG. 9B. The thinning procedure may be done with a mechanical grinding process. The following step is to remove substantially the first die substrate 76 of the first die 14D to create the first opening 32 and provide the first thinned die 14, as illustrated in FIG. 9C. Herein, removing substantially the first die substrate 76 refers to removing at least 99% of the entire first die substrate 76, and perhaps a portion of the first dielectric layer 28. In desired cases, the first die substrate 76 is fully removed. As such, the first thinned die 14 may refer to a thinned die including the first device layer 26, the first dielectric layer 28 over the first device layer 26, and the first interconnects 30 extending from the first device layer 24 to the carrier 12. Herein, the top surface of the first dielectric layer 28 is the top surface of the first thinned die 14, and is exposed to the first opening 32. Removing substantially the first die substrate 76 may be provided by an etching process with a wet/dry etchant chemistry, which may be TMAH, KOH, ACH, NaOH, or the like.

The first attach layer 22 is then applied over the top surface of the first thinned die 14 at the bottom of the first opening 32, as shown in FIG. 9D. The first attach layer 22 may be applied by roughly spreading, smoothly spreading, or special shape application methods. Some typical shapes used to apply the first attach layer 22 are: dot in the middle, two rice shaped dots, thin line, thick line, multiple lines, spiral pattern, X-shape, circle shape, circle with dot in the middle, etc. Finally, at least a portion of the first heat extractor 20 is inserted into the first opening 32 and in contact with the first attach layer 22, as shown in FIG. 9E. As such, the first heat extractor 20 is in thermal contact with the first thinned die 14 and configured to absorb the heat generated from the first thinned die 14.

Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow. 

What is claimed is:
 1. A method comprising: providing a precursor package including a carrier, a first die attached to a top surface of the carrier, and a first mold compound, which is formed over the top surface of the carrier and encapsulates the first die, wherein the first die comprises a first device layer, a first dielectric layer over the first device layer, and a first die substrate over the first dielectric layer; thinning down the first mold compound to expose a backside of the first die substrate; removing substantially the entire first die substrate to create a first opening within the first mold compound and provide a first thinned die, wherein: a first opening is formed over the first thinned die; and a top surface of the first thinned die is at a bottom of the first opening; and inserting at least a portion of a first heat extractor into the first opening, such that the first heat extractor is in thermal contact with the first thinned die, wherein the first heat extractor is formed of a metal.
 2. The method of claim 1 wherein the heat extractor is attached to the first thinned die via an attach layer, which is formed of one of a group consisting of thermal conductive epoxies, thermal conductive silicones, or alumina thermal adhesives.
 3. The method of claim 1 wherein the first heat extractor has both an X-direction dimension and a Y-direction dimension essentially the same as an X-direction dimension and a Y-direction dimension of the first opening.
 4. The method of claim 3 wherein: the first heat extractor fully fills the first opening; and a top surface of the first heat extractor and a top surface of the first mold compound are essentially at a same plane.
 5. The method of claim 3 wherein a top surface of the first heat extractor is lower than a top surface of the first mold compound.
 6. The method of claim 1 wherein the first thinned die further comprises a plurality of interconnects extending from a bottom surface of the first device layer to the top surface of the carrier.
 7. The method of claim 6 further comprising an underfilling layer, which resides between the first mold compound and the top surface of the carrier, and underfills the first thinned die between the bottom surface of the first device layer and the top surface of the carrier.
 8. The method of claim 7 wherein the underfilling layer is formed from a same material as the first mold compound.
 9. The method of claim 6 wherein the carrier comprises a plurality of carrier contacts at the top surface of the carrier, wherein each of the plurality of interconnects is electrically connected to a corresponding carrier contact in the plurality of carrier contacts.
 10. The method of claim 1 wherein the carrier is one of a group consisting of a laminate carrier, a wafer level fan out (WLFO) carrier, a wafer level fan in (WLFI) carrier, a lead frame, and a ceramic carrier.
 11. The method of claim 1 wherein a top surface of the first dielectric layer is the top surface of the first thinned die.
 12. The method of claim 1 wherein the thinning down step is provided by a mechanical grinding process.
 13. The method of claim 1 wherein the first die substrate is removed by an etching process with an etchant chemistry, which is at least one of a group consisting of Tetramethylammonium hydroxide (TMAH), potassium hydroxide (KOH), sodium hydroxide (NaOH), and acetylcholine (ACH). 